Fix compilation of the Python scripting code

3 changes are needed:

* Fix boost/python detection code in cmake

We can't detect the header without having detected python first because
when linking the app that uses the header we need to link to python, so
move the header to the code that we're trying to compile

* Fix ObjectImpType constructor, 0 is not a valid KLazyLocalizedString

* Set QT_NO_KEYWORDS since the new python has a variable called slots,
  we need to tell Qt to not use that